The present invention relates to a method and apparatus for measuring crimp in a web of crimped tow and, more particularly, it relates to such method and apparatus for quantifying the crimp of a moving crimped tow.
Crimp is the waviness of a fiber which imparts a gross waviness to the tow form of fibers. Crimp is a key factor in the processibility of many staple products and for others is important because of the bulked property it induces in the finished fiber.
The amount of crimp in a given yarn sample may be expressed as crimps per unit length. A visual crimp count can be made by counting crimps in a unit length of tow using a calibrated reticle. This method involves sampling and is limited to off-line use.
It is also known in the art to determine crimp level in fibrous tow using a light source arranged at an angle to the tow such that any reflected ray of light reflects onto a light sensing means and to make a crimp count by measuring reflected light intensity.
Existing systems convert video images into slow scan signals, remove video synchronization and use conventional analog circuits for analysis. They look at high frequency crimp on low frequency background and then amplify and convert the signals into square waves using digital comparator circuits. The frequency of the square wave and duty cycle define crimp frequency and crimp angle. These existing systems do not, however, have the ability to adequately filter out data from areas of the image with such poor contrast that peaks are missed and thus incorrect wavelengths are reported.